The purpose of this study is to expand upon a finding from a previous study in this laboratory which indicated that children with focal right cerebral hemisphere injury have difficulty with spatial construction tasks. The earlier study documented in a very general way impairment within a special cognitive domain. This project will examine the early development of spatial cognition in toddlers with right hemisphere injury at a much more detailed level of analysis. The specific aims of this project are: To define more precisely the spatial deficit identified previously; to observe whether and how the form of the deficit changes with development; and to determine if children who have difficulty with spatial construction are also delayed in the acquisition of the linguistic terms for those relations. The methodology proposed here is an adaptation of a spontaneous play task in which children are given toys and simply allowed to play. The play sessions are videotaped. The tapes serve as the basis for micro-analysis of spatial construction strategies. Data from normal 1-4 year old children, recently collected in this laboratory, indicate that developmental change in the childrens' representation of space can be analyzed along a number of different dimensions. With development children: Construct more kinds of relations and combine different relations within a single spatial grouping; build in more directions in space; use multiple spatial loci; the products of the construction process are more elaborate; and the procedures used to achieve particular groupings are more complex. We want to use these same indices of developmental change can be used to assess spatial deficit in right hemisphere damaged children. Finally, we want to examine childrens' comprehension of spatial terms, like in, on, and next to, to assess the relationship between language and thought in children with a specific conceptual disorder. Do we see delay in the acquisition of spatial terms, or can the children acquire the terms based on partial knowledge of their meaning.